1. Field of the Invention
The invention relates generally to delivery of compositions, such as therapeutic agents, to tissues.
2. Description of the Related Art
There are many variations in the routes of administration of therapeutic agents, including injection into a tissue such as muscle, intravenous injection and oral administration. When using current delivery methods, only a small percentage of the total dose of the therapeutic agent typically reaches the area where it is needed. This may be due to a variety of factors including, for example, dilution, lack of circulation in the target tissue and poor circulation in general. In some instances a therapeutically effective concentration of a pharmaceutical may be difficult or impossible to achieve in a target tissue. For example, it is often difficult to treat diabetic foot and leg ulcers with antibiotics due to the patient's poor circulation and this can lead to lower extremity amputation.
In many instances, a relatively high dose of therapeutic agent is required to provide enough of the therapeutic agent to a target region to achieve a desired therapeutic effect. Many therapeutic agents have undesirable side effects at high concentrations, and there is often a practical limit to the total dose that may be given to a patient. As a result, the concentration that can be achieved at the target site may be less than optimal. In addition, patients may require monitoring to ensure that the therapeutic agent is not causing more harm than necessary. Furthermore, therapeutic agents are often very expensive and thus the large doses required to achieve a therapeutic response increase the cost of treatment significantly.